Seat heaters?

Hey guys,
I had a question. I have an '88 Audi 5000CS Quattro....no seat heater
s! ;( But, I was wondering two things: 1. Do the seat heaters in these cars al
so heat the rear seats? I heard that when they are on for that side, that they
also heat the rear seats on that side as well, but has sensors in the seat and
can tell if someone is sitting on them and will come on depending on that. Is
this true? I don't have the seat heaters so I never knew much about them. 2.
Can seat heaters be added to my car easily (and most importantly, not too excpe
nsively!). I have just been playing with the idea of pulling the switches (con
trollers) out of a wrecked Audi and buying some new heating elements and instal
ling them myself (if I can do it without catching the car on fire!). I think t
hat all of them were pre-wired for this option. Is this true? And, does anyon
e know if this is feasible (without too much agrivation) and how much would it
cost? Any advice is apreciated....thanks.
Later,
Dan